1. Field of the Invention
The present invention relates to a substrate cleaning apparatus and a substrate cleaning method for performing scrub cleaning of a surface of a substrate such as a semiconductor wafer by bringing a contact surface of a lower end of a vertically extending cylindrical cleaning member (pencil-type cleaning member) into contact with the surface of the substrate that is being rotated in a horizontal plane in the presence of a cleaning liquid and by moving the cleaning member in one direction while the cleaning member is being rotated about its own axis. The substrate cleaning apparatus and the substrate cleaning method of the present invention can deal with a surface of a semiconductor wafer having a large diameter of 450 mm, and can be applied to a manufacturing process of a flat panel, a manufacturing process of an image sensor such as CMOS and CCD, a manufacturing process of a magnetic film for MRAM, and the like.
2. Description of the Related Art
As semiconductor devices are becoming finer these days, cleaning of various films, made of materials having different physical properties and formed on a substrate, is widely practiced. For example, in a damascene interconnect forming process for forming interconnects by filling a metal into interconnect trenches formed in an insulating film on the substrate surface, an extra metal on the substrate surface is polished away by chemical mechanical polishing (CMP) after the formation of damascene interconnects. A plurality of films such as a metal film, a barrier film and an insulating film, having different wettabilities with water, are exposed on the substrate surface after CMP.
Particles (defects) such as a residue of a slurry (slurry residue) that has been used in CMP, and metal polishing debris exist on the substrate surface having the exposed films, such as a metal film, a barrier film and an insulating film, by CMP. If cleaning of the substrate surface is insufficient and the residues remain on the substrate surface, the residues on the substrate surface may cause reliability problems such as the occurrence of leak from a residue portion, and poor adhesion. It is therefore necessary to clean the substrate surface, with a high degree of cleanliness, on which the plurality of films, such as a metal film, a bather film and an insulating film, having different wettabilities with water, are exposed.
There have been proposed various substrate cleaning apparatuses for performing scrub cleaning of a surface of a substrate such as a semiconductor wafer with a vertically extending cleaning member by moving the cleaning member in one direction while the cleaning member is being rotated about its own axis. One proposed substrate cleaning apparatus uses a cleaning member having a tapered region for acting on a surface of a substrate as disclosed in Japanese laid-open patent publication No. 2002-18368. Another proposed substrate cleaning apparatus uses a cleaning member inclined by a certain angle so that only one end portion of the cleaning member in its radial direction is brought into contact with a surface of a substrate as disclosed in Japanese laid-open patent publication No. 2000-15189. Still another proposed substrate cleaning apparatus uses a cleaning member made of natural rubber and having at least a cleaning action surface formed into a flat and smooth surface as disclosed in Japanese laid-open patent publication No. 10-312982. Further, another proposed substrate cleaning apparatus is configured to rotate a substrate and a cleaning member in respective directions that are opposite to each other as disclosed in Japanese laid-open patent publication No. 2006-737788.
In conventional common damascene interconnects, there have been used tungsten as a metal and an oxide film as an insulating film respectively. Tungsten and the oxide film have hydrophilic surface properties, having a contact angle with water of not more than 15 degrees. Recently, in damascene interconnects, there have been increasingly used copper as an interconnect metal and a so-called low-k film, having a low dielectric constant, as an insulating film. Copper and the low-k film after CMP have hydrophobic surface properties, having a contact angle with water of not less than 30 degrees. Therefore, in the case where the substrate surface on which copper and the low-k film are exposed by CMP is cleaned by scrub cleaning with a vertically extending cleaning member (pencil-type cleaning member) in the presence of a cleaning liquid, the wettability non-uniformity of the substrate surface is increased, and thus it is difficult to clean the substrate surface with a high degree of cleanliness.
Particles (defects) such as a slurry residue, remaining on a substrate surface after cleaning, may cause a lowering of the yield of a semiconductor device. Therefore, a strong demand exists for the development of a substrate cleaning apparatus and a substrate cleaning method which can clean a substrate surface with a high degree of cleanliness to reduce the number of defects remaining on the substrate surface even when the substrate surface has a hydrophobic property, such as a substrate surface after CMP in a semiconductor device whose surface condition is hydrophobic.
In the conventional general substrate cleaning apparatus for performing scrub cleaning of a surface of a substrate such as a semiconductor wafer with a vertically extending cleaning member by moving the cleaning member in one direction while the cleaning member is being rotated about its own axis, a contact pressure applied to the surface of the substrate by the cleaning member is changed by deformation of the cleaning member, but no regard is given to such change of the contact pressure. Therefore, it is difficult to clean a substantially entire area of the surface of the substrate with a high degree of cleanliness.
Particularly, a size of a silicon wafer is becoming a maximum diameter of 300 mm to a maximum diameter of 450 mm, and thus it is considered to become more difficult for the substrate cleaning apparatus to clean a substantially entire area of a surface of a large-size substrate, such as a silicon wafer having a diameter of 450 mm.